Between Master Showrooms
It is not possible to copy a Presentation from a Master Showroom to another Master Showroom. Unfortunately, since the 2 spaces are completely separate and cannot be linked, Presentations must be rebuilt from scratch.
From Master Showroom to Sub-Showroom
Presentations from the Master Showroom can be shared "down" to Sub-Showrooms underneath the Master showroom.
See Share presentations with Sub-Showrooms for more information.
However, Presentations created within a Sub-Showroom cannot be viewed in or shared with the Master Showroom.